In the discussion of the background that follows, reference is made to certain structures and/or methods. However, the following references should not be construed as an admission that these structures and/or methods constitute prior art. Applicant expressly reserves the right to demonstrate that such structures and/or methods do not qualify as prior art.
In a conventional round turning insert, a rotationally symmetrical clearance surface around a central axis extends between a top side or chip surface and an underside. The basic body shape can be cylindrical, conical or truncated conical. At the transition between the chip surface and the clearance surface there is a cutting edge that is endless and circular. During operation, only a certain part of the cutting edge engages the workpiece, e.g., along an arc. Depending on the diameter of the turning insert and the cutting depth, the arc length in contact with the workpiece varies in length, with a small arc length associated with a smaller cutting depth and a longer arc length associated with a deeper cutting depth.
Conventional seating arrangements on cutting tools for cutting inserts include a clamp that applies pressure to an insert located in a pocket of the tool holder. FIG. 1 illustrates a conventional seating arrangement 100. An insert 102 is located in a pocket 104 of a tool holder body 106. As shown, the insert 102 is round. The insert 102 is held in place by clamping forces arising from a clamp 108 contacting a top side 110 of the insert 102 and a shim 112 contacting an underside or bottom surface 114 of the insert 102. The shim 112 is generally sacrificial. In the case where the insert 102 fails, the shim 112 will absorb energy and/or itself be broken rather than the tool holder body 106. The top side 110 of the cutting insert is substantially planar and has a cutting edge 116 along the periphery where the top side transitions to the clearance surface 118. The bottom surface 114 is generally v-shaped, which is a complementary shape to the shim surface. The general design shown in FIG. 1 is sometimes referred to as a “V-Bottom” design.
The conventional seating arrangement has several limitations. For example, indexing of inserts in the V-Bottom design is limited to 180 degrees of rotation. Also for example, forces generated during back-facing cutting operations can overcome the clamping forces resulting in the insert pulling out of the tool holder. This event can cause damage to the workpiece or to the machine and possible injury to the machine operator. Further, manufacture of the V-Bottom design is generally by grinding from a larger sized blank, which has attendant waste of material.